The subject invention is directed toward the art of forming products from plastic materials and, more particularly, to a method of forming elongated, decorative strip products from thermoplastics.
The invention is especially suited for forming decorative and protective trim strips of the type applied to vehicle body panels and will be described with reference thereto; however, the invention is capable of broader application and could be used for forming similar products for other uses.
Decorative and protective trim strips of the type typically applied to the exterior surfaces of automotive vehicle body panels have been formed using many techniques. When formed from thermoplastic materials, both injection molding and extrusion processes have been used. The extrusion process offers the possibility of high production rates with relatively low tooling costs as compared to injection molding. It does, however, have certain significant disadvantages. The primary disadvantage is that the end of the extruded strip cannot have smoothly tapering contours as can readily be obtained with injection molding.
In an effort to overcome the noted disadvantage, separately molded end pieces have been joined to extruded center sections. This has not been a fully satisfactory solution since a noticeable joint line results. Further, with many plastics, especially those with metal flake type colorants, it is nearly impossible to obtain a good color match between the extruded central section and the molded end sections.